In the realm of fastening technology involving a substrate made of concrete, a distinction is made between insert elements that are cast into the concrete and anchors that are subsequently installed and that are anchored in the already hardened concrete. When it comes to the subsequently installed anchors, numerous types are known such as, for instance, expansion anchors (known, for example, from U.S. Pat. No. 5,176,481 A), screw anchors (known for example, from German patent application DE 10 2010 063675 A1), chemical anchor systems (known, for example, from U.S. Pat. No. 6,029,417 A) and undercut anchors (known, for example, from U.S. Pat. No. 6,238,128 B).
Undercut anchors are anchored in the substrate with a positive fit, which renders them particularly well-suited for dynamic loads and large crack widths, and also allows relatively high load ratings under a central traction. Moreover, undercut anchors display a load-bearing behavior similar to that of inserted head bolts. Owing to these properties, undercut anchors are considered to be very safe and reliable and this is why they are often employed for applications that call for a high degree of safety.
However, the installation of undercut anchors can be relatively complex and labor-intensive since, as a rule, the installation requires special accessories such as, for example, stop drill bits, undercut drill bits and/or installation tools. The costs incurred for these special tools often have to be included in the costs per installed fastening point, so that undercut anchors often entail higher costs per installed fastening point than in the case of other anchors such as, for instance, bolt anchors. Moreover, the installation of an undercut anchor is frequently quite time-consuming.
Due to the often relatively high costs and the often relatively labor-intensive installation, the field of application is usually restricted to the niche of applications that call for a high degree of safety or else to applications in which other types of anchor cannot be used due to the more stringent requirements, for instance, dynamic loads or large crack widths.